You’re a fit dude. You skip the bad stuff, always do #legsday, and hit the heavy bag hard. But if you want your body to continue performing like a Lamborghini, then you’ve gotta put in the high-octane fuel—that means eating the right pre-workout foods.

Think about it: A sports car still functions with regular old unleaded gas—but it won’t run as optimally or as long. Likewise, “would you expect to get to your destination if the tank was on empty?” says Jordan Mazur, R.D., coordinator of nutrition and team dietitian for the San Francisco 49ers.

For your pre-workout nutrition, you want to focus on foods that are high in carbs, moderate in protein, and low in fat and fiber. “Fat and fiber slow down digestion and can cause gastrointestinal upset during your workouts,” Mazur says. “Carbs are your main fuel source for activity and, just as important, it’s the primary fuel source for your brain. Additionally, the more substantial the meal is, the more time you want to allow for digestion, so it’s not sitting in your stomach.”